The present invention is directed to a current interrupter of the gas puffer type employing a dielectric gas forced through a nozzle into the arcing region between a pair of separable contacts.
In current interrupters of the gas puffer type where, upon contact separation, an arc extends through the throat of an insulating nozzle, the "clogging" of the nozzle by the arc has heretofore been considered undesirable. "Clogging" is a condition where the cross sectional area of the arc completely or substantially fills the orifice forming the nozzle throat. In gas puffer type interrupters, pressurized dielectric gas (for example, sulfur hexafluoride, SF.sub.6) is forced into the nozzle for discharge through the throat. The dielectric gas serves to cool the arc and the released arcing products and to minimize the hot gases that accumulate upstream of the nozzle throat. A clogged condition will prevent escape of the gas, causing a large increase in temperature in the vicinity of the arc.
Although clogging is known to occur in prior art interrupters to a limited extent, it has generally been considered undesirable. Interrupters have been designed to minimize clogging by increasing the nozzle throat and contact sizes with higher interrupter current ratings. Since the cross sectional area of an arc is dependent on many factors, including ambient pressure, temperature and other conditions, as well as the magnitude of current carried, it has been difficult to precisely predict interrupter performance to completely eliminate clogging. Prior art alternating current interrupters have therefore been designed so that clogging occurs no more than fifty percent of the time during arcing, and preferably substantially less.